Electronic payment system using check identifier and issue time for illegal acts detection

ABSTRACT

A computer-based electronic payment system, in which a payer&#39;s check issuing computer issues an electronic check having a check identifier and an issue time, where the check identifier includes a payer identifier for uniquely identifying a payer and a payment identifier for uniquely identifying a payment. Then, at a payee&#39;s check processing computer receiving the electronic check from the payer and at a bank&#39;s check processing computer receiving the electronic check transmitted from the payee, a check identifier of each electronic check accepted during a prescribed period of time prior to a current time is recorded, and a received electronic check is refused when the issue time of the received electronic check is older than the prescribed period of time past of the current time or the check identifier of the received electronic check is identical to any recorded check identifier of an already accepted electronic check, or a received electronic check is accepted when the acceptance is not refused.

This application is a continuation of application Ser. No. 08/614,253,filed Mar. 12, 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic payment system forrealizing payments on computers electronically, which is suitable for acheck acceptance system at a store for selling commercial goods inexchange for an electronic check issued by a consumer, or a checkacceptance system at a bank for transferring from a consumer's accountto a store's account according to an electronic check issued by aconsumer.

2. Description of the Background Art

An electronic check system is a conventionally proposed scheme forrealizing payments on computers electronically, which is described inKevin O'Toole: "The Internet Billing Server: Transaction ProtocolAlternatives", Carnegie Mellon University Information NetworkingInstitute, Technical Report INI TR 1994-1, April 1994; and B. CliffordNeuman: "Proxy-Based Authorization and Accounting for DistributedSystems", Proceedings of the 13th International Conference onDistributed Computing Systems, May 1993, pp. 283-291, for example.

In the electronic check system, a person responsible for payment(referred hereafter as a consumer) creates a message (referred hereafteras a check) which plays a role of a check on a computer, and sends it toa computer of a person intended to receive the payment (referredhereafter as a store) via a computer network. When the store transmitsthe received check to a computer of a bank (not necessarily limited toan ordinary bank and including any organization for managingtransactions such as a credit card company), the bank transfers aspecified amount from the consumer's account to the store's accountaccording to the check, so as to complete the payment.

Besides this electronic check system, there are other schemes forrealizing payments on computers electronically such as an on-linetransfer system and a prepaid card system, but the electronic checksystem has the following advantages in comparison with these otherschemes.

First, in the on-line transfer system, each sub-system constituting thesystem is always connected via a network with a host computer at a bankwhich provides centralized management of the electronic payments, andrequests the transfer by notifying a content of payment to the hostcomputer as soon as each payment occurs. For this reason, the on-linetransfer system involves a high communication cost, and a heavyprocessing load on the host computer. As a consequence, a cost requiredfor each transaction is high and it is inconvenient for a payment of asmall amount. In contrast, in the electronic check system, it ispossible to adopt an off-line scheme in which payments are accumulatedto some level and then transmitted to the host computer collectively, sothat there is no need for each sub-system constituting the system to bealways connected with the host computer. For this reason, a number ofcommunications can be reduced and it is convenient for a payment of asmall amount as well. Moreover, each sub-system is operable even underthe off-line environment not connected to a network all the times.

On the other hand, in the prepaid card system, the user carries a cardrecording a balance of an amount deposited in a bank in advance, andeach payment is made by subtracting an amount of each payment from therecorded balance at a time of each payment. This prepaid card system hasan advantage in that the payment can be made without requiring aconnection to the host computer each time, just as in the electroniccheck system. However, this prepaid card system is associated with aproblem in that, when the user's card is tampered by means of hardwareto alter the recorded balance illegally, it is difficult to detect aperson who committed the illegal act, and this could possibly lead to afailure of the entire system. In addition, this system is not veryconvenient for the user in that the card will be invalidated when therecorded balance becomes 0 and it requires a connection to the hostcomputer in order to validate the card again. In contrast, in theelectronic check system, the user who issued an illegal check can beidentified from an identifier of the user attached to each check, sothat the illegal user can be detected and a failure of the entire systemcan be prevented by expelling the detected illegal user from the system.

As should be apparent from the above, the electronic check system issuperior in terms of the transaction cost, the off-line performance, andthe security, and considered as a prospective candidate for anelectronic payment system to be utilized for the commercial transactionon a computer network targeting general consumers, which is attractingmuch attention recently.

A check used in this electronic check system usually contains a checkidentifier (ID) for uniquely identifying each check, in addition to anamount of payment. Moreover, it is common to assign the check identifierin a form containing an identifier of the consumer and an identifier ofthe store, in order to prevent conflicts among identifiers.

A check is provided in a form capable of authenticating that it iscreated by a particular consumer by means of the digital signature (seeWhitfield Diffie and Martin E. Hellman: "New Directions inCryptography", IEEE Transactions on Information Theory, Vol. IT-22, No.6, pp. 644-654, November 1976, for example). Consequently, a personother than that particular consumer can read the content of the check bydecrypting it, but cannot create a new check as if it is created by thatparticular consumer in an attempt to receive the payment illegally.

However, in this electronic check system, it is still possible to makean illegal copy of the check, and for this reason, the possibilities forthe following two types of illegality cannot be prevented.

First, the store can commit the illegal act called "double charge". Thisis an illegal act in which the store transmits the check received fromthe consumer to the bank more than once, so as to obtain an amountgreater than an amount to be actually paid by receiving the same paymenta number of times.

On the other hand, the consumer can commit the illegal act called"double issue". This is an illegal act in which the consumer issues thesame check more than once. Normally, the checks have identifiers whichare mutually different from each other, but this identifier is to beassigned by the consumer. Consequently, it is possible for the consumerto issue a check for a certain payment using the same identifier as thatalready used for another payment, and gives these checks with theidentical identifier to the respective stores. This "double issue" byitself may not cause any trouble as long as the bank makes the transfersamong the accounts as usual by regarding these checks with the identicalidentifier as different checks. However, from the bank's point of view,the "double charge" and the "double issue" are indistinguishable.Consequently, the consumer can make the "double issue" and then claimthat it is the "double charge" by the store, so as to pay only an amountless than an amount to be actually paid.

In order to prevent this "double issue", it is possible for the store torecord the identifiers of all the checks accepted in past and refuse toaccept a check issued by a consumer by judging it as the "double issue"when this check uses the same identifier as that already used at thatstore.

In addition, assuming that the "double issue" is prevented in thismanner, it is also possible to prevent the "double charge" similarly.Namely, it is possible for the bank to record the identifiers of all thechecks accepted in past and refuse to accept a check transmitted from astore by judging it as the "double charge" when this check uses the sameidentifier as that already used at that bank (on an assumption that the"double issue" is already prevented and therefore cannot occur).

However, although it is possible to prevent the "double issue" and the"double charge" in this manner in principle, in order to be able todetect the "double issue" and the "double charge" without a failure, itis necessary to preserve records of all the checks used in past. Namely,in order to detect the "double issue" and the "double charge", it isnecessary for the store and the bank to preserve an unlimited number ofrecords of the checks, and these records can be enormously voluminousfor the store and the bank which have a large number of customers.Therefore, apart from a need for a very large capacity memory device, aprocessing load required for searching out a particular identifier fromthis very large capacity memory device would also become appreciable.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide anelectronic payment system capable of suppressing a capacity of a memorydevice required for recording the identifiers of the already used checksand thereby reducing a required search time, while enabling thedetection of the illegal copy of the electronic check without a failure.

According to one aspect of the present invention there is provided acomputer-based electronic check processing system, comprising: receivingmeans for receiving an electronic check having a check identifier and anissue time, the check identifier including a payer identifier foruniquely identifying a payer and a payment identifier for uniquelyidentifying a payment; memory means for recording a check identifier ofeach electronic check accepted during a prescribed period of time priorto a current time; and acceptance judgement means for refusing anacceptance of a received electronic check when the issue time of thereceived electronic check is older than the prescribed period of timeprior to the current time or the check identifier of the receivedelectronic check is identical to the check identifier of any alreadyaccepted electronic check recorded in the memory means, and accepting areceived electronic check when the acceptance is not refused.

According to another aspect of the present invention there is provided amethod of computer-based electronic check processing, comprising thesteps of: receiving an electronic check having a check identifier and anissue time, the check identifier including a payer identifier foruniquely identifying a payer and a payment identifier for uniquelyidentifying a payment; recording a check identifier of each electroniccheck accepted during a prescribed period of time prior to a currenttime; and refusing an acceptance of a received electronic check when theissue time of the received electronic check is older than the prescribedperiod of time prior to the current time or the check identifier of thereceived electronic check is identical to the check identifier of anyalready accepted electronic check recorded by the recording step, andaccepting a received electronic check when the acceptance is notrefused.

According to another aspect of the present invention there is providedan article of manufacture, comprising: a computer usable medium havingcomputer readable program code means embodied therein for causing acomputer to function as an electronic payment processing system forprocessing an electronic check, the computer readable program meansincluding: first computer readable program code means for causing thecomputer to receive an electronic check having a check identifier and anissue time, the check identifier including a payer identifier foruniquely identifying a payer and a payment identifier for uniquelyidentifying a payment; second computer readable program code means forcausing the computer to record a check identifier of each electroniccheck accepted during a prescribed period of time prior to a currenttime; and third computer readable program code means for causing thecomputer to refuse an acceptance of a received electronic check when theissue time of the received electronic check is older than the prescribedperiod of time prior to the current time or the check identifier of thereceived electronic check is identical to the check identifier of anyalready accepted electronic check recorded by the second computerreadable program code means, and accepting a received electronic checkwhen the acceptance is not refused.

According to another aspect of the present invention there is provided acomputer-based electronic payment system, comprising: a payer's checkissuing computer for issuing an electronic check having a checkidentifier and an issue time, the check identifier including a payeridentifier for uniquely identifying a payer and a payment identifier foruniquely identifying a payment; a payee's check processing computer forreceiving the electronic check from the payer's check issuing computer,recording a check identifier of each electronic check accepted by thepayee's check processing computer during a first prescribed period oftime prior to a current time, refusing an acceptance of a receivedelectronic check when the issue time of the received electronic check isolder than the first prescribed period of time prior to the current timeor the check identifier of the received electronic check is identical toany recorded check identifier of an already accepted electronic check,accepting a received electronic check when the acceptance is notrefused, and transmitting each accepted electronic check; and atransaction executing computer for receiving the electronic checktransmitted from the payee's check processing computer, recording acheck identifier of each electronic check accepted by the transactionexecuting computer during a second prescribed period of time prior tothe current time, refusing an acceptance of a transmitted electroniccheck when the issue time of the transmitted electronic check is olderthan the second prescribed period of time prior to the current time orthe check identifier of the transmitted electronic check is identical toany recorded check identifier of an already accepted electronic check,accepting a received electronic check when the acceptance is notrefused, and transferring a specified amount from a specified payer'saccount to a specified payee's account according to each acceptedelectronic check.

According to another aspect of the present invention there is provided amethod of computer-based electronic payment, comprising the steps of:(a) at a payer's check issuing computer, issuing an electronic checkhaving a check identifier and an issue time, the check identifierincluding a payer identifier for uniquely identifying a payer and apayment identifier for uniquely identifying a payment; (b) at a payee'scheck processing computer, receiving the electronic check from thepayer's check issuing computer, recording a check identifier of eachelectronic check accepted by the payee's check processing computerduring a first prescribed period of time prior to a current time,refusing an acceptance of a received electronic check when the issuetime of the received electronic check is older than the first prescribedperiod of time prior to the current time or the check identifier of thereceived electronic check is identical to any recorded check identifierof an already accepted electronic check, accepting a received electroniccheck when the acceptance is not refused, and transmitting each acceptedelectronic check; and (c) at a transaction executing computer, receivingthe electronic check transmitted from the payee's check processingcomputer, recording a check identifier of each electronic check acceptedby the transaction executing computer during a second prescribed periodof time prior to the current time, refusing an acceptance of atransmitted electronic check when the issue time of the transmittedelectronic check is older than the second prescribed period of timeprior to the current time or the check identifier of the transmittedelectronic check is identical to any recorded check identifier of analready accepted electronic check, accepting a received electronic checkwhen the acceptance is not refused, and transferring a specified amountfrom a specified payer's account to a specified payee's accountaccording to each accepted electronic check.

Other features and advantages of the present invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of an overall configuration of anelectronic payment system according to the present invention.

FIG. 2 is a block diagram of a detailed configuration of a consumer'scheck issuing system in the electronic payment system of FIG. 1according to the first embodiment.

FIG. 3 is a block diagram of a detailed configuration of a store's checkprocessing system in the electronic payment system of FIG. 1 accordingto the first embodiment.

FIG. 4 is a block diagram of a detailed configuration of a bank's checkprocessing system in the electronic payment system of FIG. 1 accordingto the first embodiment.

FIG. 5 is a block diagram of a detailed configuration of a bank's checkprocessing system in the electronic payment system of FIG. 1 accordingto the second embodiment.

FIG. 6 is a block diagram of a detailed configuration of a consumer'scheck issuing system in the electronic payment system of FIG . 1according to the third embodiment.

FIG. 7 is a block diagram of a detailed configuration of a store's checkprocessing system in the electronic payment system of FIG. 1 accordingto the third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, the preferred embodiments of an electronic payment system accordingto the present invention will be described in detail.

First, the main features of the present invention will be brieflysummarized.

In the present invention, the records of information for identifyingchecks issued during a prescribed period of time up to a current timeare recorded at the store and the bank. When a check is received from aconsumer or a store, whether this check has already been accepted beforeor not is judged according to these records. Consequently, it isimpossible to perpetrate a "double issue" or "double charge" by givingthe same check more than once.

Also, at a time of receiving a check, the issue date and time of thecheck are examined, and if the issue date and time of the check areolder than a prescribed period of time prior to current date and time,the acceptance of this check will be refused by judging it as an expiredone. For this reason, the "double issue" or the "double charge" usingthe old check which is already deleted from the records can also bedetected.

In this manner, the "double issue" and the "double charge" can beprevented according to the present invention. Moreover, it is onlynecessary to keep each record during the above described prescribedperiod of time, and the records of the checks issued earlier than thatcan be discarded. For this reason, a capacity of the memory devicerequired for keeping records of the already used checks can be reduced,and therefore a search time required in examining whether each check hasalready been accepted before or not can be shortened.

Here, the fact that the information concerning the issue date and timeof the check is integrally incorporated within the check itself impliesthat a correspondence between the information concerning the issue dateand time and the check itself will be maintained throughout the entiredistribution process of the check (from the issuance until thetransfer), and that the information concerning the issue date and timecannot be tampered.

More specifically, the issue date and time are included within a maintext of the check which also contains an identifier of a consumer, anidentification number unique to each payment, and an amount of eachpayment, and then the issuer of the check (payer) digitally signs thecheck, so that it is impossible to separate the issue date and time fromthe check itself to tamper it and pass the tampered check again at anystage in the distribution route of the check. For example, it ispossible to examine the issue date and time by decrypting the check evenby the store's system, but at a time of passing the check to the bank,the digitally signed check itself is to be passed. Consequently, even ifthe store tampers the issue date and time of the check and passes thetampered check again, it is impossible for the store to digitally signthe check correctly, so that the illegal act by the store can bedetected by the bank.

Now, with references to FIG. 1 to FIG. 4, the first embodiment of anelectronic payment system according to the present invention will bedescribed in detail.

The electronic payment system of this embodiment has an overallconfiguration as shown in FIG. 1, which comprises a consumer's checkissuing system 100, a store's check processing system 200, and a bank'scheck processing system 300, where the check issued by the consumer'scheck issuing system 100 will be examined by the store's checkprocessing system 200 and the bank's check processing system 300 withregards to its issue date and time, etc. In addition, the store's checkprocessing system 200 has a temporary memory unit 22 for temporarilystoring checks before passing them to the bank's check processing system300.

In the following, each of these sub-systems constituting the electronicpayment system of FIG. 1 will be described one by one.

FIG. 2 shows a detailed configuration of the consumer's check issuingsystem 100 in the electronic payment system of FIG. 1.

In this consumer's check issuing system 100 of FIG. 2, an identifierformed by combining a consumer's identifier and a check serial number isused as a check identifier. The consumer identifier of a consumer whoowns this consumer's check issuing system 100 is stored in a consumeridentifier memory unit 1 in advance. A check serial number memory unit 2stores a previously issued check serial number, and outputs a new checkserial number by adding one to the stored serial number every time a newcheck is to be issued.

By generating the check identifier in this manner, an identifier alreadyused before will not be used again, and it will be impossible for anyother consumer to issue a check with the same identifier as that of acheck issued by this consumer. These statements may not necessarily betrue, however, when this consumer himself commits an illegal act of"double issue" on this consumer's check issuing system 100,

In this consumer's check issuing system 100, a check main textproduction unit 3 produces a check main text containing the consumeridentifier, the check serial number, an amount of payment, a storeidentifier for specifying a receiver of the check, and issue date andtime. Then, a digital signature production unit 4 produces a digitalsignature by using a consumer's private encryption key which is assignedto each consumer in advance and stored in a consumer's privateencryption key memory unit 5, and attaches the produced digitalsignature to the check main text, to form a digitally signed check 101.

Here, the check main text containing the issue date and time is producedby entering current date and time generated by a current date and timegeneration unit 7. Also, the check main text containing the storeidentifier is produced by entering an identifier of a store specified bythe consumer through a user input/output unit 9 among store identifiersstored in a store identifier memory unit 8. The amount of payment isentered into the check main text according to an amount specified by theconsumer through the user input/output unit 9 or an amount specified inadvance.

The digitally signed check 101 so produced is then transmitted to thestore's check processing system 200 via a communication line or a memorymedium.

Also, a consumer's private decryption key 102, which is issued by a keydistribution center and digitally signed by a certification authority,and which is necessary in authenticating the check, is stored in aconsumer's private decryption key memory unit 6 and transmitted alongthe digitally signed check 101 to the store's check processing system200.

FIG. 3 shows a detailed configuration of the store's check processingsystem 200 in the electronic payment system of FIG. 1.

In this store's check processing system 200 of FIG. 3, when thedigitally signed check 101 is received from the consumer's check issuingsystem 100, the consumer's private decryption key 102 received along thedigitally signed check 101 is authenticated at a consumer's privatedecryption key authentication unit 11 using a key distribution center'sprivate decryption key stored in a key distribution center's privatedecryption key memory unit 10. Then, when the received consumer'sprivate decryption key 102 is verified as a proper consumer's privatedecryption key distributed by the key distribution center, the digitalsignature of the digitally signed check 101 is authenticated at adigital signature authentication unit 12 using the received consumer'sprivate decryption key 102.

After these authentications are successfully completed, the issue dateand time written in the check main text is taken out, and compared withcurrent date and time obtained from a current date and time generationunit 13 to see if the issue date and time are older than a prescribedperiod of time prior to the current date and time at a date and timecomparison unit 14. If the issue date and time are older, the acceptanceof this check is refused by judging it as expired at an acceptancejudgement unit 15. A notice 103 (including a notice 104 from the bank'scheck processing system 300 to be described below) regarding the refusalof the acceptance is then notified to the consumer's check issuingsystem 100 via a communication line or a memory medium. This notice 103will be given to the consumer via the user input/output unit 9. Whenthis notice 103 is given, the consumer can issue a new electronic checkagain according to the procedure described above.

In addition, the store identifier specifying a receiver of the check istaken out from the check main text, and compared with this store's ownidentifier stored in a store identifier memory unit 16 to see if theycoincide at a store identifier comparison unit 17. If they do notcoincide, the acceptance of this check is refused at the acceptancejudgement unit 15.

In addition, the check identifier is taken out from the check main text,and a check identifier search unit 21 searches for this check identifierin a check identifier memory unit 20 storing the check identifiers ofthe checks already accepted by the store during the above describedprescribed period of time used by the date and time comparison unit 14.If the same check identifier is found in the check identifier memoryunit 20, it implies that the check has already been accepted by thestore before, so that the acceptance of this check is refused by judgingit as the "double issue" at the acceptance judgement unit 15.

In addition, the amount of payment is taken out from the check maintext, and compared with an amount of payment to be received by thistransaction stored in an amount of payment memory unit 18 to see if theycoincide at an amount of payment comparison unit 19. If they do notcoincide, the acceptance of this check is refused at the acceptancejudgement unit 15.

The check identifier of the accepted check is stored in the checkidentifier memory unit 20. In this check identifier memory unit 20, thecheck identifier of the check whose issue date and time are older thanthe above described prescribed period of time past of the current dateand time will be discarded.

When the check is accepted by the acceptance judgement unit 15, theaccepted check 101 and the corresponding consumer's private decryptionkey 102 are temporarily stored in a check and consumer's privatedecryption key temporary memory unit 22. Then, whenever the storewishes, the check 101 and the consumer's private decryption key 102 inthe check and consumer's private decryption key temporary memory unit 22are transmitted to the bank's check processing system 300. Here, thecheck 101 and the consumer's private decryption key 102 to betransmitted to the bank's check processing system 300 are those receivedfrom the consumer's check issuing system 100 at the store's checkprocessing system 200 as they are.

With this configuration, the store's check processing system 200 candetect an occurrence of the "double issue" by the consumer with respectto the same store.

FIG. 4 shows a detailed configuration of the bank's check processingsystem 300 in the electronic payment system of FIG. 1.

In this bank's check processing system 300 of FIG. 4, when the digitallysigned check 101 is received from the store's check processing system200, the consumer's private decryption key 102 received along thedigitally signed check 101 is authenticated at a consumer's privatedecryption key authentication unit 34 using a key distribution center'sprivate decryption key stored in a key distribution center's privatedecryption key memory unit 33. Then, when the received consumer'sprivate decryption key 102 is verified as a proper consumer's privatedecryption key distributed by the key distribution center, the digitalsignature of the digitally signed check 101 is authenticated at adigital signature authentication unit 35 using the received consumer'sprivate decryption key 102.

After these authentications are successfully completed, the issue dateand time written in the check main text is taken out, and compared withcurrent date and time obtained from a current date and time generationunit 36 to see if the issue date and time are older than a prescribedperiod of time prior to the current date and time or not at a date andtime comparison unit 37. Here, the prescribed period of time used inthis date and time comparison unit 37 may not be the same as that usedin the store's check processing system 200 as will be mentioned below.If the issue date and time are older, the acceptance of this check isrefused by judging it as an expired one at an acceptance judgement unit38. A notice 104 regarding the refusal of the acceptance is thennotified to the store's check processing system 200 via a communicationline or a memory medium. This notice 104 may be notified to theconsumer's check issuing system 100 as the notice 103 from the store'scheck processing system 200 described above, or given directly to thethe consumer's check issuing system 100 in parallel to a notification tothe store's check processing system 200 from the bank's check processingsystem 300.

In addition, the check identifier is taken out from the check main text,and a check identifier search unit 31 searches for this check identifierin a check identifier memory unit 30 storing the check identifiers ofthe checks already accepted by the bank during the above describedprescribed period of time used by the date and time comparison unit 37.If the same check identifier is found in the check identifier memoryunit 30, it implies that the check has already been accepted by the bankbefore, so that the acceptance of this check is refused by judging it asthe "double issue" or the "double charge" at the acceptance judgementunit 38.

The check identifier of the accepted check is stored in the checkidentifier memory unit 30. In this check identifier memory unit 30, thecheck identifier of the check whose issue date and time are older thanthe above described prescribed period of time prior to the current dateand time will be discarded.

Note that the check issued by the consumer arrives at the bank by beingtemporarily stored in the check and consumer's private decryption keytemporary memory unit 22 at the store, and transmitted to the bank onlyat a timing desired by the store, so that it is rather usual to receivethe check at the bank after some time has elapsed since the issue dateand time of the check. Consequently, it is preferable to set theprescribed period of time used by the date and time comparison unit 37and the check identifier memory unit 30 in the bank's check processingsystem 300 longer than the prescribed period of time used by the dateand time comparison unit 14 and the check identifier memory unit 20 inthe store's check processing system 200, according to how long itusually takes for the store to transmit the checks to the bank.

When the check is accepted by the acceptance judgement unit 38, atransfer control unit 24 carries out a transfer of the amount of paymentspecified in the check main text, from an account 23 of the consumerspecified by the check identifier contained in the check main text to anaccount 25 of the store specified by the store identifier contained inthe check main text.

With this configuration, it is possible for the bank's check processingsystem 300 to detect an occurrence of either the "double issue" by theconsumer with respect to different stores or the "double charge" by thestore.

Consequently, in this electronic payment system, the "double issue" bythe consumer with respect to the same store can be detected at thestore's check processing system 200, and the "double issue" by theconsumer with respect to different stores and the "double charge" by thestore can be detected at the bank's check processing system 300, so thatthe illegal acts of "double issue" and "double charge" can be prevented.

Moreover, it is only necessary to keep each check identifier during aprescribed period of time, and the check identifiers of the checksissued earlier than that can be discarded, so that a capacity of thememory device required for keeping records of the already used checkscan be reduced, and therefore a search time required in examiningwhether each check has already been accepted before or not can beshortened.

Next, with reference to FIG. 5, the second embodiment of an electronicpayment system according to the present invention will be described indetail.

In the first embodiment described above, among the "double issue" thatcan be made by the consumer, the "double issue" with respect todifferent stores by the consumer cannot be detected at the store's checkprocessing system. Moreover, at the bank's check processing system, anoccurrence of either one of the "double issue" by the consumer withrespect to different stores and the "double charge" by the store can bedetected, but which one of these has occurred cannot be judged.

This second embodiment is directed to a modification of the firstembodiment described above, in which it is made possible for the bank'scheck processing system to judge which one of the "double issue" by theconsumer with respect to different stores and the "double charge" by thestore has occurred, by recording the entire check main text rather thanjust the check identifier at the bank's check processing system. Here,the overall configuration of the electronic payment system issubstantially similar to that of FIG. 1 except that the bank's checkprocessing system 300 is to be replaced by the bank's check processingsystem 300A shown in FIG. 5, as follows.

FIG. 5 shows a detailed configuration of the bank's check processingsystem 300A in this second embodiment.

Instead of the check identifier memory unit 30 and the check identifiersearch unit 31 in the configuration of FIG. 4, this configuration ofFIG. 5 has a check memory unit 40 and a check search unit 41, by meansof which the entire check main text including the check identifier isstored and searched, respectively. The other elements of this bank'scheck processing system 300A of FIG. 5 are similar to those of thebank's check processing system 300 of FIG. 4.

The check search unit 41 searches for the check main text of the checkwhich has the same check identifier as that taken out from the check 101received from the store's check processing system 200, in the checkmemory unit 40 storing the check main texts of the checks alreadyaccepted by the bank during the above described prescribed period oftime used by the date and time comparison unit 37.

When the check main text with the identical check identifier is found inthe check memory unit 40, the found check main text is compared with thecheck main text received from the store's check processing system 200,and if they coincide, it can be judged that it is the "double charge" bythe store, whereas if they do not coincide, it can be judged that it isthe "double issue" with respect to different stores by the consumer.

Thus, with this configuration, it is possible for the bank's checkprocessing system 300A to distinguishably detect the "double issue" bythe consumer with respect to different stores and the "double charge" bythe store.

Next, with references to FIG. 6 and FIG. 7, the third embodiment of anelectronic payment system according to the present invention will bedescribed in detail.

In the second embodiment described above, it is made possible for thebank's check processing system to detect the "double issue" by theconsumer with respect to different stores. Instead, this thirdembodiment is directed to a modification of the first embodimentdescribed above, in which it is made possible for the store's checkprocessing system to detect the "double issue" by the consumer withrespect to different stores, by modifying a manner of generating thecheck identifier. Here, the overall configuration of the electronicpayment system is substantially similar to that of FIG. 1 except thatthe consumer's check issuing system 100 is to be replaced by theconsumer's check issuing system 100 shown in FIG. 6, and the store'scheck processing system 200 is to be replaced by the store's checkprocessing system 200A shown in FIG. 7, as follows.

FIG. 6 shows a detailed configuration of the consumer's check issuingsystem 100A in this third embodiment.

In this consumer's check issuing system 100A of FIG. 6, the checkidentifier is generated by further combining the store identifier storedin the store identifier memory unit 8 to a combination of the consumeridentifier and the check serial number. In this case, the storeidentifier is contained in the check identifier, so that there is noneed to enter the store identifier itself as an independent item in thecheck main text. The other elements of this consumer's check issuingsystem 100A of FIG. 6 are similar to those of the consumer's checkissuing system 100 of FIG. 2.

FIG. 7 shows a detailed configuration of the store's check processingsystem 200A in this third embodiment.

In this store's check processing system 200A of FIG. 7, there is noindependent item for the store identifier in the check main text, sothat the store identifier comparison 50 compares the store identifierextracted from the check identifier in the check main text with thisstore's own identifier stored in the store identifier memory unit 16.The other elements of this store's check processing system 200A of FIG.7 are similar to those of the store's check processing system 200 ofFIG. 3.

With these configurations, when the consumer attempts to issue theidentical checks to different stores, at least one of these identicalchecks is going to have the store identifier different from that of thestore which received it, so that the "double issue" by the user will beimmediately detected at the store which received one of the identicalchecks, and the acceptance of the check will be refused. Note that thisthird embodiment is characterized by issuing the check by including thestore identifier in addition to the consumer identifier and the checkserial number. In this manner, it becomes practically impossible for theconsumer to issue the identical checks to different stores, because thechecks issued to different stores require different store identifiers,and the different store identifiers imply different check identifiers inthis case.

As described according to the present invention, the "double issue" bythe consumer and the "double charge" by the store can be detected at thestore or the bank without a failure, so that it is possible to preventthe illegal acts such as "double issue" and "double charge" in theelectronic payment system.

Moreover, it is only necessary to store and search the records of thechecks issued during a prescribed period of time prior of the currentdate and time, and there is no need to store and search an unlimitedamount of records of the checks, so that there is no need to require anenormous cost for the storing and searching of the records of thechecks, and it becomes possible to realize a safe electronic paymentsystem at a lower cost.

It is to be noted that the above described embodiments according to thepresent invention may be conveniently implemented using a conventionalgeneral purpose digital computer programmed according to the teachingsof the present specification, as will be apparent to those skilled inthe computer art. Appropriate software coding can readily be prepared byskilled programmers based on the teachings of the present disclosure, aswill be apparent to those skilled in the software art.

For example, the functions of each one of the consumer's checkprocessing system of FIG. 2 or FIG. 6, the store's check processingsystem of FIG. 3 or FIG. 7, and the bank's check processing system ofFIG. 4 or FIG. 5 can be implemented as a separate computer program forcontrolling the general purpose digital computer to realize therespective functions as described above. Such a computer program can beimplemented as a software package to be installed on a general purposedigital computer in practice.

Such a software package can be a computer program product which employsa storage medium including stored computer code which is used to programa computer to perform the disclosed function and process of the presentinvention. The storage medium may include, but is not limited to, anytype of conventional floppy disks, optical disks, CD-ROMs,magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnetic or opticalcards, or any other suitable media for storing electronic instructions.

It is to be noted that, besides those already mentioned above, manymodifications and variations of the above embodiments may be madewithout departing from the novel and advantageous features of thepresent invention. Accordingly, all such modifications and variationsare intended to be included within the scope of the appended claims.

What is claimed is:
 1. A computer-based electronic check processingsystem for a transaction executing party that receives and processeselectronic checks transmitted from payees of the electronic checks, thesystem comprising:receiving means for receiving an electronic checkhaving a check identifier and an issue time, the check identifierincluding a payer identifier for uniquely identifying a payer and apayment identifier for uniquely identifying a payment; memory means forrecording a check main text including a check identifier of eachelectronic check accepted during a prescribed period of time prior to acurrent time and a payee identifier associated with the check; andacceptance judgement means for refusing an acceptance of a receivedelectronic check when the issue time of the received electronic check isolder than the prescribed period of time prior to the current time or ifthe check identifier of the received electronic check is identical tothe check identifier of any already accepted electronic check recordedin the memory means, for judging the received electronic check as adouble issue check by a payer with respect to different payees when thecheck identifier of the received electronic check is identical to thecheck identifier of an already accepted electronic check recorded in thememory means and the check main text of the received electronic check isnot identical to the check main text of the already accepted electroniccheck recorded in the memory means, and for accepting a receivedelectronic check when the acceptance is not refused.
 2. The system ofclaim 1, further comprising transfer means for transferring a specifiedamount from a specified payer's account to a specified payee's accountin accordance with each electronic check accepted by the acceptancejudgement means.
 3. The system of claim 1, wherein the acceptancejudgement means judges a received electronic check as a double issuecheck by a payer or a double charge check by a payee when the checkidentifier of the received electronic check is identical to the checkidentifier of an already accepted electronic check recorded in thememory means.
 4. The system of claim 1, wherein the memory means recordsa check main text of each already accepted electronic check includingthe check identifier of each already accepted electronic check.
 5. Thesystem of claim 1, wherein the acceptance judgement means judges areceived electronic check as a double charge check by a payee when thecheck identifier of the received electronic check is identical to thecheck identifier of an already accepted electronic check recorded in thememory means and the check main text of the received electronic check isalso identical to the check main text of the already accepted electroniccheck recorded in the memory means.
 6. The system of claim 1, whereinthe receiving means receives each electronic check having the checkidentifier which also includes a payee identifier for uniquelyidentifying a payee.
 7. The system of claim 1, wherein the issue timeindicates at least a date on which the electronic check is issued.
 8. Amethod of computer-based electronic check processing for a transactionexecuting party that receives and processes electronic checkstransmitted from payees of the electronic checks, the method comprisingthe steps of:receiving an electronic check having a check identifier andan issue time, the check identifier including a payer identifier foruniquely identifying a payer and a payment identifier for uniquelyidentifying a payment; recording a check main text including a checkidentifier of each electronic check accepted during a prescribed periodof time prior to a current time and a payee identifier associated withthe check; refusing an acceptance of a received electronic check whenthe issue time of the received electronic check is older than theprescribed period of time prior to the current time or if the checkidentifier of the received electronic check is identical to the checkidentifier of any already accepted electronic check recorded by therecording step, judging the received electronic check as a double issuecheck by a payer with respect to different payees when the checkidentifier of the received electronic check is identical to the checkidentifier of an already accepted electronic check recorded by therecording step and the check main text of the received electronic checkis not identical to the check main text of the already acceptedelectronic check recorded by the recording step, and accepting areceived electronic check when the acceptance is not refused.
 9. Themethod of claim 8, further comprising the step of transferring aspecified amount from a specified payer's account to a specified payee'saccount in accordance with each electronic check accepted by theaccepting step.
 10. The method of claim 8, wherein the accepting stepjudges a received electronic check as a double issue check by a payer ora double charge check by a payee when the check identifier of thereceived electronic check is identical to the check identifier of analready accepted electronic check recorded by the recording step. 11.The method of claim 8, wherein the recording step records a check maintext of each already accepted electronic check including the checkidentifier of each already accepted electronic check.
 12. The method ofclaim 8, wherein the accepting step judges a received electronic checkas a double charge check by a payee when the check identifier of thereceived electronic check is identical to the check identifier of analready accepted electronic check recorded by the recording step and thecheck main text of the received electronic check is also identical tothe check main text of the already accepted electronic check recorded bythe recording step.
 13. The method of claim 8, wherein the receivingstep receives each electronic check having the check identifier whichalso includes a payee identifier for uniquely identifying a payee. 14.The method of claim 8, wherein the issue time indicates at least a dateon which the electronic check is issued.
 15. An article of manufacturecomprising a computer usable medium having computer readable programcode means embodied therein for causing a computer to function as anelectronic payment processing system for a transaction executing partythat receives and processes electronic checks transmitted from payees ofthe electronic checks, the computer readable program code meansincluding:first computer readable program code means for causing thecomputer to receive an electronic check having a check identifier and anissue time, the check identifier including a payer identifier foruniquely identifying a payer and a payment identifier for uniquelyidentifying a payment; second computer readable program code means forcausing the computer to record a check main text including a checkidentifier of each electronic check accepted during a prescribed periodof time prior to a current time and a payee identifier associated withthe check; and third computer readable program code means for causingthe computer to refuse an acceptance of a received electronic check whenthe issue time of the received electronic check is older than theprescribed period of time prior to the current time or if the checkidentifier of the received electronic check is identical to the checkidentifier of any already accepted electronic check recorded by thesecond computer readable program code means, judge the receivedelectronic check as a double issue check by a payer with respect todifferent payees when the check identifier of the received electroniccheck is identical to the check identifier of an already acceptedelectronic check recorded by the second computer readable program codemeans and the check main text of the received electronic check is notidentical to the check main text of the already accepted electroniccheck recorded by the second computer readable program code means, andaccept a received electronic check when the acceptance is not refused.16. The article of manufacture of claim 15, further comprisingadditional computer readable program code means for causing the computerto transfer a specified amount from a specified payer's account to aspecified payee's account in accordance with each electronic checkaccepted by the third computer readable program code means.
 17. Thearticle of manufacture of claim 15, wherein the third computer readableprogram code means judges a received electronic check as a double issuecheck by a payer or a double charge check by a payee when the checkidentifier of the received electronic check is identical to the checkidentifier of an already accepted electronic check recorded by thesecond computer readable program code means.
 18. The article ofmanufacture of claim 15, wherein the second computer readable programcode means records a check main text of each already accepted electroniccheck including the check identifier of each already accepted electroniccheck.
 19. The article of manufacture of claim 15, wherein the thirdcomputer readable program code means judges a received electronic checkas a double charge check by a payee when the check identifier of thereceived electronic check is identical to the check identifier of analready accepted electronic check recorded by the second computerreadable program code means and the check main text of the receivedelectronic check is also identical to the check main text of the alreadyaccepted electronic check recorded by the second computer readableprogram code means.
 20. The article of manufacture of claim 15, whereinthe first computer readable program code means receives each electroniccheck having the check identifier which also includes a payee identifierfor uniquely identifying a payee.
 21. The article of manufacture ofclaim 15, wherein the issue time indicates at least a date on which theelectronic check is issued.
 22. A computer-based electronic checkprocessing system for a payee who receives and processes electronicchecks from payers of the electronic checks, the systemcomprising:receiving means for receiving an electronic check having acheck identifier and an issue time, the check identifier including apayee identifier for uniquely identifying a payee, a payer identifierfor uniquely identifying a payer and a payment identifier for uniquelyidentifying a payment; memory means for recording a check identifier ofeach electronic check accepted during a prescribed period of time priorto a current time; and acceptance judgement means for refusing anacceptance of a received electronic check when the issue time of thereceived electronic check is older than the prescribed period of timeprior to the current time or if the check identifier of the receivedelectronic check is identical to the check identifier of any alreadyaccepted electronic check recorded in the memory means, for judging thereceived electronic check as a double issue check by a payer withrespect to different payees when the payee identifier specified by thecheck identifier of the received electronic check does not coincide witha required payee identifier given to the system in advance, and foraccepting a received electronic check when the acceptance is notrefused.
 23. The system of claim 22, further comprising transmissionmeans for transmitting each electronic check accepted by the acceptancejudgement means to another electronic check processing system forfurther processing the electronic check.
 24. The system of claim 22,wherein the acceptance judgement means also refuses an acceptance of areceived electronic check when an amount of payment specified by thereceived electronic check does not coincide with a required amount ofpayment given to the system in advance.
 25. The system of claim 22,wherein the issue time indicates at least a date on which the electroniccheck is issued.
 26. A method of computer-based electronic checkprocessing for a payee who receives and processes electronic checks frompayers of the electronic checks, the method comprising the stepsof:receiving an electronic check having a check identifier and an issuetime, the check identifier including a payee identifier for uniquelyidentifying a payee, a payer identifier for uniquely identifying a payerand a payment identifier for uniquely identifying a payment; recording acheck identifier of each electronic check accepted during a prescribedperiod of time prior to a current time; refusing an acceptance of areceived electronic check when the issue time of the received electroniccheck is older than the prescribed period of time prior to the currenttime or if the check identifier of the received electronic check isidentical to the check identifier of any already accepted electroniccheck recorded by the recording step, judging the received electroniccheck as a double issue check by a payer with respect to differentpayees when the payee identifier specified by the check identifier ofthe received electronic check does not coincide with a required payeeidentifier given to the system in advance, and accepting a receivedelectronic check when the acceptance is not refused.
 27. The method ofclaim 26, further comprising the step of transmitting each electroniccheck accepted by the accepting step to another electronic checkprocessing system for further processing the electronic check.
 28. Themethod of claim 26, wherein the accepting step also refuses anacceptance of a received electronic check when an amount of paymentspecified by the received electronic check does not coincide with arequired amount of payment given in advance.
 29. The method of claim 26,wherein the issue time indicates at least a date on which the electroniccheck is issued.
 30. An article of manufacture, comprising:a computerusable medium having computer readable program code means embodiedtherein for causing a computer to function as an electronic paymentprocessing system for a payee who receives and processes electronicchecks from payers of the electronic checks, the computer readableprogram code means including:first computer readable program code meansfor causing the computer to receive an electronic check having a checkidentifier and an issue time, the check identifier including a payeeidentifier for uniquely identifying a payee, a payer identifier foruniquely identifying a payer and a payment identifier for uniquelyidentifying a payment; second computer readable program code means forcausing the computer to record a check identifier of each electroniccheck accepted during a prescribed period of time prior to a currenttime; and third computer readable program code means for causing thecomputer to refuse an acceptance of a received electronic check when theissue time of the received electronic check is older than the prescribedperiod of time prior to the current time or if the check identifier ofthe received electronic check is identical to the check identifier ofany already accepted electronic check recorded by the second computerreadable program code means, judge the received electronic check as adouble issue check by a payer with respect to different payees when thepayee identifier specified by the check identifier of the receivedelectronic check does not coincide with a required payee identifiergiven to the system in advance, and accept a received electronic checkwhen the acceptance is not refused.
 31. The article of manufacture ofclaim 30, further comprising additional computer readable program codemeans for causing the computer to transmit each electronic checkaccepted by the third computer readable program code means to anotherelectronic check processing system for further processing the electroniccheck.
 32. The article of manufacture of claim 30, wherein the thirdcomputer readable program code means also refuses an acceptance of areceived electronic check when an amount of payment specified by thereceived electronic check does not coincide with a required amount ofpayment given in advance.
 33. The article of manufacture of claim 30,wherein the issue time indicates at least a date on which the electroniccheck is issued.